Sheet wrapping avoidable fixing apparatus and image forming apparatus

0001This is a continuation of Ser. No. 10/158,852, filed Jun. 3, 2002, now U.S. Pat. No. 6,795,676.

CROSS-REFERENCE TO RELATED APPLICATIONS

0002This application claims priority under 35 USC § 119 to Japanese Patent Application Nos. 2001-222186, 2001-167346, and 2001-261814 filed on Jul. 23, 2001, Jun. 01, 2001, Aug. 30, 2001, respectively, the entire contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

00031. Field of the Invention

0004The present invention relates to a fixing apparatus and an image forming apparatus including a heat fixing member and a pressure applying member pressure contacting the fixing member.

0005In particular, the present invention relates to a fixing apparatus and image forming apparatus capable of fixing a toner image to a recording member while directing and conveying the recording member to and through a nip formed between the fixing member and pressure applying member in such a manner that the toner image contacts the fixing member.

00062. Discussion of the Background

0007It has been well known that a fixing apparatus of the above-described type is adopted in an image forming apparatus, such as a copier, a printer, a facsimile, a combined machine having at least one of them, and etc. In such a type of the fixing apparatus, since the toner fuses when passing the nip formed between the fixing and pressure applying members, the toner likely functions as an adhesive agent and the recording member ejected from the nip is not separated and wraps around the surface of the fixing member. In particular, in an image forming apparatus forming a full-color image, since different color toner images are superimposed on a recording member and fixed by a fixing apparatus, toner necessarily fuses in the nip, and thus the adhesive force of the toner increases. As a result, the recording member more readily wraps around the fixing member.

0008In the past, a separation member including a plurality of separation claws has been configured to contact a surface of a fixing member and separate a recording member ejected from a nip from the surface of the fixing member in order for the recording member not to wrap around the surface of the fixing member. However, since the separation claw contacts the surface of the fixing member via its tip, the surface likely is cut (e.g, damaged). As a result, a mark appears on a toner image after passing through the nip in accordance with the cut, and resulting in inferior toner image quality as a result of fixing.

0009To avoid such disadvantage, a fixing apparatus is proposed to arrange a separation claw separating from a surface of the fixing member. However, a recording member ejected from the nip likely enters into a gap formed between the fixing member and separation claw while sticking the surface of the fixing member. As a result, the separation function of the recording member is weakened and wrapping likelihood of the recording member around the fixing member increases.

0010In addition, there exists a case when a fixed toner image is formed on a backside surface of the recording member carrying a toner image on the other side to be fixed. In such situation, since the toner image on the backside surface is fused by heat while passing through the nip, the recording member likely wraps around the surface of the pressure applying member. To avoid such problem, a separation claw preferably contacts the surface of the pressure applying member. However, a similar problem arises as described in the above.

SUMMARY OF THE INVENTION

0011The present invention has been made in view of such problems and to address and resolve such problems. Accordingly, it is an object of the present invention to provide a novel fixing apparatus including a fixing member and a pressure applying member configured to pressure contact the fixing member. The fixing apparatus directs and conveys a recording member through a nip formed between the fixing member and pressure applying member so that a toner image carried on the recording member can contact the fixing member so as to be fixed thereto with heat and pressure. The fixing apparatus is configured to direct a margin formed in a transfer direction tip of the recording member across a virtual linear extension line drawn from a downstream end to an upstream end both in the nip toward the pressure applying member, when only the margin exits from the nip. A fixing member side separation device is provided so as to separate the recording member ejected from the nip not contacting the surface of the fixing apparatus. In addition, a gap between the downstream end of the nip and the tip of the fixing member side separation device is set smaller than the width of the margin of the downstream end.

0012In yet another embodiment, the JIS-A hardness of the surface of the pressure applying member of the nip at the downstream end may be larger than that of the downstream end of the fixing member.

0013In another embodiment, a pressure applying member side separation device is provided with its tip contacting the surface of the pressure applying member.

0014In yet another embodiment, JIS-A hardness of the surface of the fixing member in the nip in the downstream end is substantially the same to that of the downstream end of the surface of the pressure applying member.

0015In yet another embodiment, the JIS-A hardness of the surface of the fixing member of the nip in the downstream end is higher than that of the downstream end of the pressure applying member.

0016In yet another embodiment, a fixing member side separation device is provided with its tip contacting the surface of the fixing member.

0017In yet another embodiment, gap maintaining members are provided on respective tips of the fixing member side separation devices disposed in a direction perpendicular to the transfer direction so as to contact the surface of a non-transfer member passage area of the fixing member so that a gap formed between the tip of the fixing member side separation device and the surface of the fixing member is maintained.

0018In yet another embodiment, gap maintaining members are also provided on respective tips of the pressure applying member side separation devices so as to contact the surface of a non-transfer member passage area of the pressure applying member so that a gap formed between the tip of the pressure applying member side separation device and the surface of the pressure applying member is maintained.

0019In yet another embodiment, the fixing member side separation device is a single separation member type.

0020In yet another embodiment, the pressure applying member side separation device is a single separation member type.

0021In yet another embodiment, the fixing member side separation device includes an opening for ventilation.

0022In yet another embodiment, the pressure applying member side separation device includes an opening for ventilation.

0023In yet another embodiment, the fixing member side separation device is formed from a sheet like separation member, and is biased by a tension applying member in a direction perpendicular to the transfer direction.

0024In yet another embodiment, the pressure applying member side separation device is formed from a sheet like separation member, and is biased be a tension applying member in a direction perpendicular to the transfer direction.

0025In yet another embodiment, toner includes, at least, plastic, colorant, and wax.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by the following detailed description when considered in connection with the accompanying drawings, wherein:

<figref idref="DRAWINGS">FIG. 1</figref> is a schematic cross sectional diagram for illustrating one example of an image forming apparatus;

<figref idref="DRAWINGS">FIG. 2</figref> is a cross sectional view for illustrating one example of a fixing apparatus;

<figref idref="DRAWINGS">FIG. 3</figref> is an enlarged view for illustrating the fixing apparatus illustrated in <figref idref="DRAWINGS">FIG. 2</figref>;

<figref idref="DRAWINGS">FIG. 4</figref> is an explanatory chart for illustrating a margin on a recording member;

<figref idref="DRAWINGS">FIG. 5</figref> is a cross sectional view for illustrating another fixing apparatus:

<figref idref="DRAWINGS">FIG. 6</figref> is a cross sectional view for illustrating still another fixing apparatus:

<figref idref="DRAWINGS">FIG. 7</figref> is an enlarged explanatory chart for illustrating the fixing apparatus of <figref idref="DRAWINGS">FIG. 6</figref>;

<figref idref="DRAWINGS">FIG. 8</figref> is a cross sectional view for illustrating still another fixing apparatus;

<figref idref="DRAWINGS">FIG. 9</figref> is a cross sectional view for illustrating yet another fixing apparatus

<figref idref="DRAWINGS">FIG. 10</figref> is a cross sectional view for illustrating yet another fixing apparatus

<figref idref="DRAWINGS">FIG. 11</figref> is a plan view for illustrating one example of a separation member supporting apparatus;

<figref idref="DRAWINGS">FIG. 12</figref> is a perspective view for illustrating a condition in that a gap-maintaining member of <figref idref="DRAWINGS">FIG. 11</figref> contacts the surface of the fixing roller;

<figref idref="DRAWINGS">FIG. 13</figref> is an explanatory diagram for illustrating a still another fixing apparatus;

<figref idref="DRAWINGS">FIG. 14</figref> is a schematic chart for illustrating a color image forming apparatus installing one exemplary configuration of a fixing apparatus according to the present invention;

<figref idref="DRAWINGS">FIG. 15</figref> is a schematic enlarged chart for illustrating a configuration of the fixing apparatus utilized in the image forming apparatus of <figref idref="DRAWINGS">FIG. 14</figref>;

<figref idref="DRAWINGS">FIG. 16</figref> is a schematic enlarged configuration chart for illustrating a fixing roller and pressure applying roller utilized in the fixing apparatus of <figref idref="DRAWINGS">FIG. 15</figref>;

<figref idref="DRAWINGS">FIG. 17</figref> is an exploded perspective view for illustrating a fixing roller, and a separation sheet, and a guide member utilized in the fixing apparatus of <figref idref="DRAWINGS">FIG. 15</figref>;

<figref idref="DRAWINGS">FIGS. 18A and 18B</figref> are enlarged cross sectional views each for illustrating a guide member utilized in the fixing apparatus of <figref idref="DRAWINGS">FIG. 15</figref>, and conditions before and after the separation sheet is attached;

<figref idref="DRAWINGS">FIG. 19</figref> is an enlarged cross sectional view-for illustrating a tip of the separation sheet utilized in the fixing apparatus of <figref idref="DRAWINGS">FIG. 15</figref>;

<figref idref="DRAWINGS">FIG. 20</figref> is a schematic chart for illustrating a configuration of a color image forming apparatus including the fixing apparatus of the other embodiment of the present invention;

<figref idref="DRAWINGS">FIG. 21</figref> is an enlarged schematic view for illustrating a fixing apparatus utilized in the color image forming apparatus of <figref idref="DRAWINGS">FIG. 20</figref>;

<figref idref="DRAWINGS">FIG. 22</figref> is a side view for illustrating a relevant part configuration of an L-type bracket and separation sheet utilized in the fixing apparatus according to the present invention;

<figref idref="DRAWINGS">FIG. 23</figref> is a plan view for illustrating a relevant part configuration of the fixing apparatus of <figref idref="DRAWINGS">FIG. 22</figref>; and

<figref idref="DRAWINGS">FIG. 24</figref> is a side view for illustrating a relevant part configuration of a fixing roller and pressure-applying device utilized in the other embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

0051Referring now to the drawings, wherein like reference numerals and marks designate identical or corresponding parts throughout several views, in particular, in <figref idref="DRAWINGS">FIG. 1</figref>, a schematic image forming apparatus <b>1</b> is illustrated using a vertical cross sectional view. The image forming apparatus <b>1</b> may include an image formation member <b>2</b> for forming a toner image on a recording member, a sheet feeding device <b>3</b> for feeding recording members to the image formation member <b>2</b>, and a fixing apparatus <b>4</b> for fixing a toner image formed on the recording member. An exemplary configuration of the fixing apparatus <b>4</b> simply illustrated by a block may be described later in detail. The image formation device <b>2</b> may include a drum shaped photo-conductive member <b>5</b> serving as one example of an image carrier, and the surface of the PC member <b>5</b> is charged in a prescribed polarity while rotating clockwise. To the charged surface, a laser beam “L” ejected from a laser writing unit <b>7</b> serving as one example of an exposure apparatus may be modulated and irradiated. Thereby, a latent image may be formed on the PC member surface. The latent image may then be visualized by the developing apparatus <b>8</b> so as to be a toner image. The toner image may then be transferred by a transfer apparatus <b>9</b> onto a recording member transferred from the sheet feeding apparatus <b>3</b>. A cleaning apparatus <b>10</b> may remove remaining and sticking toner on the PC drum surface after the toner image transfer.

0052The sheet-feeding device <b>3</b> may include a cassette <b>11</b> containing recording members P such as transfer sheets, plastic sheets, etc. The recording members P may be fed from the cassette <b>11</b> from the upper most one by rotation of a feeding roller <b>12</b>. The recording member may then be fed to a transfer station formed between the PC member <b>5</b> and transfer apparatus <b>9</b>. Then, the toner image on the PC member <b>5</b> may be transferred onto recording member as described above. Thus, the recording member carrying the toner image in such a manner may then be transferred through the fixing apparatus <b>4</b> as illustrated by an arrow “A”, and passes therethrough. At that time, the toner image on the recording member may be fixed. The recording-member passing through the fixing apparatus <b>4</b> may then be ejected on a tray <b>14</b> outside the image forming apparatus. <figref idref="DRAWINGS">FIG. 2</figref> is an enlarged cross sectional view illustrating one example of a fixing apparatus <b>4</b>. The fixing apparatus <b>4</b> may include a fixing roller <b>15</b> as a fixing member, and a pressure roller a pressure <b>16</b> pressure contacting the fixing roller <b>15</b> as a pressure applying member. A nip “N” may be formed due to pressure contact of these rollers <b>15</b> and <b>16</b>. The fixing roller <b>15</b> and pressure roller <b>16</b> may each be formed of a cylindrical shape having a cross section having circular outer circumference. In an illustrated example, these rollers <b>15</b> and <b>16</b> may each be formed in a hollow cylindrical shape. The fixing roller <b>15</b> may rotate clockwise, and the pressure roller <b>16</b> may rotate counterclockwise.

0053The nip N formed between these rollers <b>15</b> and <b>16</b> may be controlled by a heating device to maintain an appropriate temperature for fixing a toner image. In the example, halogen heaters <b>17</b> and <b>18</b> may be disposed inside the fixing and pressure rollers <b>15</b> and <b>16</b> as heat sources, respectively. These heaters <b>17</b> and <b>18</b> may be controlled by a temperature control device (not shown) to turn ON/OFF in order to maintain the appropriate temperature.

0054The recording member “P” carrying a not yet fused toner image “T” may be conveyed to the fixing apparatus <b>4</b> in a direction illustrated by an arrow “A”. The recording member “P” may pass through the nip “N” while directing the toner image “T” to the surface of the fixing roller <b>15</b>.

0055Thereby, the toner image “T” on the recording member “P” may be fixed thereonto by the heat and pressure.

0056A basic configuration employed in the below described various examples will be substantially the same to that described above. Instead of using the above-described configuration of rollers <b>15</b> and <b>16</b> of <figref idref="DRAWINGS">FIG. 2</figref>, the fixing member can be formed by a rotating seamless fixing belt wound and driven by a guide member as described later. The pressure applying member can also be a seamless pressure belt wound and driven by a guide member. In such a manner, these fixing and pressure applying members can be various conformations.

0057Now, when a toner image “T” carried on the recording member “P” passes through the nip “N” of the fixing apparatus <b>4</b> illustrated in <figref idref="DRAWINGS">FIG. 2</figref>, the toner may fuse therein. To avoid the recording member “P” ejected from the nip “N” from wrapping around the surface of the fixing roller <b>15</b> due to adhesive force of the toner, the below described configuration may be adopted.

0058<figref idref="DRAWINGS">FIG. 3</figref> is an enlarged explanatory chart illustrating a nip “N” formed between the fixing and pressure rollers <b>15</b> and <b>16</b>, and a recording member “P” passing therethrough. As illustrated in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, a fixing member side separation device <b>19</b> for separating a recording member “P” ejected from the nip “N” from the fixing member (e.g. the fixing roller <b>15</b> in this example) may be arranged in the vicinity of an outlet of the nip “N” while being separated from the surface of the fixing member. Such a fixing member side separation device <b>19</b> may be shaped in appropriate, such as a sheet state separation member <b>20</b>.

0059A toner image may be formed on an image region, slashed and having a note “IA”, of the recording member as illustrated in <figref idref="DRAWINGS">FIG. 4</figref>. A margin “M” where no toner image is formed may appear in a portion outside the image region “IA”. The recording member “P” may be transferred in a direction shown by an arrow “A” and invade the fixing apparatus <b>4</b>. A width of a blank “M<b>1</b>” located in a tip in the transfer direction “A” is supposed to be “W” ranging from about 2 mm to about 5 mm. <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, and also <figref idref="DRAWINGS">FIGS. 5 to 10</figref>, illustrate a condition where only the tip blank “M<b>1</b>” is just ejected from the nip “N”. Now, if a gap formed between an outlet end of the nip N (i.e., a downstream end NE) and a tip, facing the fixing member, of the fixing member separation device <b>19</b> is supposed to be “G” as illustrated in <figref idref="DRAWINGS">FIG. 3</figref>, the gap G may be set smaller in size than the width “W”. Accordingly, when only the entire margin M<b>1</b> of the tip of the recording member P exits from the nip N as illustrated in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, the tip of the fixing member side separation device <b>19</b> may enter and position at a space formed between the margin M<b>1</b> and fixing roller <b>15</b>.

0060The JIS-A (Japanese Industrial Standard-A) hardness of the surface of the pressure roller <b>16</b> may be set higher than that of the surface of the fixing roller <b>15</b>, and is preferably twenty to forty times thereof. In such a manner, by setting a surface hardness of these rollers <b>15</b> and <b>16</b>, the pressure roller <b>16</b> may break into and deform the surface of the fixing roller <b>15</b> side the surface by pressure as illustrated in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>. Specifically, a section of the fixing roller <b>15</b> pressure contacting the pressure roller <b>16</b> may elastically be deformed in a compression condition.

0061Accordingly, as illustrated in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, when only the margin M<b>1</b> exits from the nip “N”, the margin “M<b>1</b>” may take a posture along with the surface of the pressure roller <b>16</b>, and is largely deviated from the surface of the fixing roller <b>15</b>. Since no toner image is formed in the tip margin M<b>1</b>, the margin M<b>1</b> may not tend to stick to the surface of the fixing roller <b>15</b> due to a toner sticking force. In addition, the margin M<b>1</b> may be ejected from the nip “N” almost in parallel to the surface of the pressure roller <b>16</b>. Simultaneously, since the margin M<b>1</b> is largely distanced from the surface of the fixing roller <b>15</b>, the margin M<b>1</b> of the recording member P may not wrap around the surface of the fixing roller <b>15</b>. If a straight line virtually drawn from the downstream end NE to upstream end NS is supposed to be “LA”, and when only the tip margin M<b>1</b> exits from the nip “N”, the margin M<b>1</b> is directed to the pressure applying member (the pressure roller <b>16</b> in this example) across the elongation LA extended from the straight line LAA.

0062When the recording member P is further transferred in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, the image region IA illustrated in <figref idref="DRAWINGS">FIG. 4</figref> may start to be ejected from the nip N. Then, since the recording member P sticks or tend to stick to the surface of the fixing roller <b>15</b> due to an adhesive force of the toner on the image region IA, the recording member P is strained to the fixing roller <b>15</b> side. Such a tendency may be prominent when a flexible recording member such as a thin paper is utilized.

0063However, since the fixing member side separation device <b>19</b> is disposed in the vicinity of the fixing roller <b>15</b> the recording member P may collide and is then guided by the fixing member side separation device <b>19</b> as illustrated in <figref idref="DRAWINGS">FIG. 3</figref> by a dotted line, and thus is prevented from wrapping around the surface of fixing roller <b>15</b>. Even if the fixing member side separation device <b>19</b> is arranged being separated from the surface of the fixing roller <b>15</b>, since the gap G is set as smaller than the width W of the margin M<b>1</b>, the recording member P strained toward the fixing roller <b>15</b> may be prevented from passing through the gap P and wrapping around the surface of the fixing roller <b>15</b>. The recording member P exiting from the nip N may subsequently is guided and transferred by the fixing member side separation device <b>19</b> located upside and guiding member <b>21</b> located downside.

0064Thus, since the recording member P ejected from the nip N is prevented from wrapping around the surface of the fixing roller <b>15</b>, and the fixing member side separation device <b>19</b> does not contact the surface of the fixing roller <b>15</b>, a problem that the surface of the fixing roller <b>15</b>, which has a low hardness and is easily damaged by the fixing member side separation device <b>19</b>, may be blocked.

0065The image forming apparatus of <figref idref="DRAWINGS">FIG. 1</figref> is configured to form a mono color toner image, typically, a black toner image on the recording member P. However, since for example, yellow, magenta, cyan, and black toner images are superimposed on the recording member, and are fixed by a fixing apparatus in an image forming apparatus, the recording member readily particularly wraps around the fixing member. However, by also applying the above-described configuration in the color image forming apparatus, the recording member may avoid from wrapping around the fixing member while the fixing member is prevented from being damaged.

0066Now, a specific construction of the fixing apparatus <b>4</b> is described with reference to <figref idref="DRAWINGS">FIG. 2</figref>. The fixing roller <b>15</b> may include a core metal bar <b>23</b>, an elastic layer <b>24</b> laminated on the outer circumferential surface of the core metal <b>23</b>, and a release agent layer <b>25</b> on the outer circumferential surface of the elastic layer <b>24</b>. The outer diameter of the fixing roller <b>15</b> may be 40 mm, for example. The core metal <b>23</b> may include an iron hollow roller having an outer diameter of 34 mm and a thickness of 1 mm, for example. The elastic layer <b>24</b> may be made of silicon rubber, for example, whose thickness is 3 mm. The release agent layer <b>25</b> may be formed by a PFA tube having a thickness of from 10 to 30 μm. By employing such a release agent layer <b>25</b>, adhesion of a recording member P to the surface of the fixing roller due to toner adhesive force can be avoided. The pressure roller <b>16</b> may include a core metal bar <b>26</b> formed by an iron hollow roller having an outer diameter of 38 mm and a thickness of 1 mm, an elastic layer <b>27</b> laminated on the outer circumferential surface of the core metal <b>26</b>, and a release agent layer <b>28</b> on the outer circumferential surface of the elastic layer <b>27</b>. The elastic layer <b>27</b> may be made of silicon rubber, for example, whose thickness is 1 mm. The release agent layer <b>28</b> may be formed by a PFA tube having a thickness of from 10 to 30 μm.

0067Respective surface hardness of the fixing roller <b>15</b> and pressure roller <b>16</b> may be set to 45 and 80 degrees by the Japanese Industrial. Standard “JIS—A”. In such a manner, since the pressure roller <b>16</b> is harder, the fixing roller <b>15</b> may be elastically deformed while the pressure roller <b>16</b> breaks into the surface of the fixing roller <b>15</b>. Simultaneously, a nip “N” may be formed along an outer shape of the pressure roller <b>16</b>.

0068In the fixing apparatus <b>4</b> of <figref idref="DRAWINGS">FIG. 5</figref>, a fixing member may be formed from a fixing belt <b>15</b>A. The fixing belt <b>15</b>A may be wound around a guide member including a pair of guide rollers <b>15</b>B and <b>15</b>C. However, a number of the guide members can be more than three. Further, similar to the illustration of the fixing apparatus of <figref idref="DRAWINGS">FIG. 2</figref>, the pressure applying member may include a hollow pressure roller <b>16</b>. The pressure roller <b>16</b> and guide rollers <b>15</b>B and <b>15</b>C may be cylindrical like having cross sections having circular outer circumferences. In the example of <figref idref="DRAWINGS">FIG. 5</figref>, respective rollers <b>15</b>B, <b>15</b>C, and <b>16</b> may be formed in hollow cylindrical shapes. The pressure roller <b>16</b> may pressure contact one of the guide rollers <b>15</b>B via the fixing belt <b>15</b>A. Accordingly, the outer peripheral surface of the pressure roller <b>16</b> may pressure contact the outer circumferential surface of the fixing belt <b>15</b>A while forming a nip “N”. Respective guide rollers <b>15</b>B and <b>15</b>C and pressure roller <b>16</b> may rotate in directions shown by arrows, and thereby, the fixing belt <b>15</b>A may be rotated in the direction shown by an arrow B. Thus, when the seamless fixing belt <b>15</b>A is rotated, the guide rollers <b>15</b>B and <b>15</b>C may function of guiding the seamless fixing belt <b>15</b>A. In addition, the guide roller <b>15</b>B opposing to the pressure roller <b>16</b> may farm the nip “N” in cooperation with the pressure roller <b>16</b>. The other guide roller <b>15</b>C may function as a tension roller for applying tension to the fixing belt <b>15</b>A. As described later, a guide member other than the guide roller can be employed and the fixing belt <b>15</b>A can be wound around the other guide member. Otherwise, the pressure roller <b>16</b> can pressure contact a plurality of guide members via the fixing belt <b>15</b>A. Specifically, the fixing member is constituted by the seamless fixing belt wound and rotated by a plurality of guide members, and the pressure applying member is formed from a pressure roller pressure contacting and rotated by the at least one guide members via the fixing belt.

0069By recognizing the importance of the above-described functions of both guide rollers <b>15</b>B and <b>15</b>C, one side guide roller <b>15</b>B will be termed by an opposing roller, and another guide roller <b>15</b>C will be termed by a tension roller when required in the below described description.

0070Further, in the respective tension roller <b>15</b>C and pressure roller <b>16</b> of the fixing apparatus of <figref idref="DRAWINGS">FIG. 5</figref>, heaters <b>17</b>A and <b>18</b> may be provided so as to heat the fixing belt <b>15</b>A and pressure roller <b>16</b>. Power supplying to the heaters <b>17</b>A and <b>18</b> may be turned ON and OFF, so that a temperature of the nip “N” may be maintained in an appropriate range suitable for fixing a toner image.

0071Also in this example, a recording member P carrying a toner image “T” to be fixed may pass through the nip “N” while the toner image “T” contacts the surface of the fixing belt <b>15</b>A as shown by an arrow A.

0072Thus, the toner image “T” may be fixed onto the recording member P by the heat and pressure.

0073Also the JIS-A surface hardness of the pressure roller <b>16</b> in the fixing apparatus <b>4</b> of <figref idref="DRAWINGS">FIG. 5</figref> may be set higher than, that of the surface of the fixing belt wound around the guide member (e.g. an opposing roller <b>15</b>B in the drawing). Accordingly, as similar to the fixing apparatus of <figref idref="DRAWINGS">FIG. 2</figref>, when only the tip margin M<b>1</b> of a recording member exits from the nip N in the fixing apparatus <b>4</b> of <figref idref="DRAWINGS">FIG. 5</figref>, the tip margin M<b>1</b> may be directed to the pressure applying member (pressure roller <b>16</b> in the drawing) side across an extension line LAA extended from the straight line LA, which is drawn from the downstream end NE to the upstream end NS of the nip N, toward the downstream side. In addition, the fixing member side separation device <b>19</b> for separating a recording member P ejected from the nip N from the surface of the fixing member composed of the fixing belt <b>15</b>A may be arranged in a non-contact condition while opposing to the surface of the fixing member. Also, the gap G formed between the tip of the fixing member side separation device <b>19</b> facing the fixing member and the downstream end NE may be set smaller in size than a width W of the margin M<b>1</b> of the tip of the recording member P in the sheet transfer direction.

0074Thus, the wrapping of the recording member P around the fixing member composed of the fixing belt <b>15</b>A as well as damaging on the fixing belt <b>15</b>A by the fixing member side separation device <b>19</b> can be absolutely or substantially avoided substantially in the same manner as in the fixing apparatuses of <figref idref="DRAWINGS">FIGS. 2 and 3</figref>. Simultaneously, the quality of a toner image after fixing may be improved and a life of the fixing belt <b>15</b>A may be prolonged. Very similar to the fixing apparatuses of <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, the recording member P ejected from the nip “N” may then be guided and is transferred by the fixing member side separation device <b>19</b> together with the guide member <b>21</b>, and is ejected onto the tray <b>14</b> (see <figref idref="DRAWINGS">FIG. 1</figref>).

0075A specific configuration of the fixing apparatus <b>4</b> is now described with reference to <figref idref="DRAWINGS">FIG. 5</figref>. Both the opposing roller <b>15</b> and pressure roller <b>16</b> may be similarly constructed to those in the fixing apparatus of <figref idref="DRAWINGS">FIG. 2</figref>. The fixing belt <b>15</b>A may include a base substance made of polyimide plastic having a thickness of 50 μm, for example, and silicon rubber laminated on the base substance. The silicon rubber may have a thickness of 0.2 mm and JIS-A hardness of 30 degree. Also included may be a release agent layer made of PFA having a thickness of 5 μm and coated on the silicon rubber. Further, the nip “N” of <figref idref="DRAWINGS">FIG. 5</figref> may be formed from a first nip portion where the pressure roller <b>16</b> does not oppose to the opposing roller <b>15</b>B and only contacts the fixing belt <b>15</b>A, and a second nip portion where the pressure roller <b>16</b> contact the opposing roller <b>15</b>B via the fixing belt <b>15</b>A. Accordingly, the nip N may range widely in a circulation direction of the fixing belt <b>15</b>A, and the pressure contacting force caused between the pressure roller <b>16</b> and fixing belt <b>15</b>A may be relatively small. In addition, an appropriate temperature of the nip N may be lowered.

0076Further, since the fixing roller <b>15</b> of the fixing apparatus of <figref idref="DRAWINGS">FIG. 2</figref> is heated by the heater <b>17</b>A from inside the rubber elastic layer <b>24</b> having low heat conductivity, a long idling time is required when the fixing apparatus is started up and the fixing roller <b>15</b> reaches a prescribed temperature suitable for fixing a toner image. In the fixing apparatus of <figref idref="DRAWINGS">FIG. 5</figref>, however, since not only the thin and small heat capacity fixing belt <b>15</b>A is utilized for the fixing member, and the fixing belt <b>15</b>B is not heated from inside the opposing roller <b>15</b>B and is rather heated by the heater <b>17</b>A disposed in the thin tension roller <b>15</b>C, the idling time required when the fixing belt <b>15</b>A reaches the prescribed temperature can be minimized. In the fixing apparatuses of <figref idref="DRAWINGS">FIGS. 2 and 5</figref>, in order to direct the tip margin M<b>1</b> of the recording member P to the pressure applying member side across the extension line LAA when only the tip margin M<b>1</b> exits from the nip N the surface hardness of the fixing member constituted by the fixing roller <b>15</b> and fixing belt <b>15</b>A, and the pressure applying member constituted by the pressure roller <b>16</b> may be set to levels as described earlier. However, if the fixing member is formed from the fixing belt <b>15</b>A, the hardness of the surface of the fixing member may be represented by a portion of the surface of the fixing belt when the fixing belt is wound by the opposing roller <b>15</b>B as described-above. Importantly, when the JIS-A hardness of the surface of the pressure applying member at, the downstream end NE in the nip N is set higher than that of the surface of the pressure applying member at the upstream end NS and only the margin M<b>1</b> exits from the nip N, the margin M<b>1</b> may be directed to the pressure applying member side across the extension line LAA.

0077Additional fixing apparatuses are now described with reference to <figref idref="DRAWINGS">FIGS. 6 and 7</figref>. These fixing apparatuses may each be substantially similar to that illustrated in <figref idref="DRAWINGS">FIG. 2</figref>. Thus, description of both basis configuration and function are omitted while the same codes in <figref idref="DRAWINGS">FIG. 2</figref> are assigned to respective corresponding sections in the fixing apparatus of <figref idref="DRAWINGS">FIG. 6</figref>.

0078Various differences of the fixing apparatuses of <figref idref="DRAWINGS">FIGS. 6 and 7</figref> from that of <figref idref="DRAWINGS">FIG. 2</figref> may be that a surface hardness of JIS-A of a fixing member composed of a fixing roller <b>15</b> is substantially the same to that of the JIS-A of a pressure applying member composed of a pressure roller <b>16</b>. By setting the respective surface hardness of the fixing roller <b>15</b> and pressure roller <b>16</b> in such a manner, both the rollers <b>15</b> and <b>16</b> may be deformed to be substantially flat key pressure in the nip N formed therebetween, thereby a substantially straight nip N may be formed. As a result as illustrated in <figref idref="DRAWINGS">FIG. 7</figref>, when only the tip margin M<b>1</b> exits from the nip N, it may be directed along the extension line LBB extended from the straight line LB drawn from the downstream end NE and the upstream end NS of the nip N. Further, a fixing member side separation device <b>19</b> for separating a recording member P ejected from the nip N from the surface of the fixing member composed of the fixing roller <b>15</b> may also be arranged in a non-contact condition opposing to the surface of the fixing member. Simultaneously, a gap G, formed between the downstream end NE in the nip N and the tip (chip) of the fixing member side separation device <b>19</b> facing the fixing member, may be set to be smaller in size than the width W of the margin M<b>1</b>.

0079As illustrated in <figref idref="DRAWINGS">FIGS. 6 and 7</figref>, since a toner image is not formed on the margin M<b>1</b>, the margin M<b>1</b> may not tend to adhere to the surface of the fixing roller <b>15</b> due to an adherence force when only exiting from the nip N, and is ejected from the nip N along the extension line LBB. Thus, the margin M<b>1</b> of the recording member P may not wrap around the surface of the fixing roller <b>7</b>.<b>5</b> in such a condition. When the recording member in the condition illustrated in <figref idref="DRAWINGS">FIGS. 6 and 7</figref> is further transferred in a direction shown by an arrow A, an image area IA of <figref idref="DRAWINGS">FIG. 4</figref> may start being ejected from the nip N, and the recording member P may adhere or tend to adhere to the surface of the fixing roller <b>15</b> due to an adhesive force of the toner on the image area IA. Thus, the recording member P may be pulled toward the fixing roller <b>15</b>. However, since the fixing member side separation device <b>19</b> is disposed in the vicinity of the fixing roller <b>15</b>, the recording member P may collide and is guided by the fixing member side separation device <b>19</b>. As a result, wrapping of the recording member P around the surface of the fixing roller <b>15</b> maybe prevented. Simultaneously, the fixing member side separation device <b>19</b> is separately disposed from the surface of the fixing roller <b>15</b>. Since the gap G is set smaller in size than the width W of the margin M<b>1</b>, the recording member P pulled toward the fixing roller <b>15</b> due to the toner adhesive force may be prevented from passage through the gap G and wrapping around the surface of the fixing roller while adhering to the surface of the fixing roller. The recording member P passing through the fixing apparatus <b>4</b> may then be ejected onto the tray <b>14</b> of <figref idref="DRAWINGS">FIG. 1</figref>.

0080Also in the fixing apparatus of <figref idref="DRAWINGS">FIGS. 6 and 7</figref> , the recording member P ejected from the nip N may be avoided from wrapping around the surface of the fixing roller <b>15</b>. In addition, since the fixing member side separation device <b>19</b> does not contact the surface of the fixing roller <b>15</b>, damage on the surface of the fixing roller <b>15</b>, which has a low hardness and is easily damaged by the fixing member side separation device <b>19</b>, may be avoided. In addition, since the nip N is of a flat shape, the recording member ejected from the nip may advantageously hardly be curled when compared with a case when the nip N is curved. Both the fixing roller <b>15</b> and pressure roller <b>16</b> of the fixing apparatus of <figref idref="DRAWINGS">FIG. 6</figref> can be similarly constituted to that of the fixing roller <b>16</b> of <figref idref="DRAWINGS">FIG. 2</figref>. The surface hardness of the fixing roller <b>15</b> and pressure roller <b>16</b> of the fixing apparatus of <figref idref="DRAWINGS">FIG. 6</figref> can be 45 degree in terms of the JIS-A. Since respective surface hardness of the fixing roller <b>15</b> and pressure roller <b>16</b> are substantially the same to each other, the nip N may be formed substantially flat.

0081Still another fixing apparatus <b>4</b> may be described with reference to <figref idref="DRAWINGS">FIG. 8</figref>. The basic configuration of a shown fixing apparatus <b>4</b> may be substantially the same to that of <figref idref="DRAWINGS">FIG. 5</figref>. In contrast to the tension roller <b>15</b>C positioning a right side of the opposing roller <b>15</b>B in <figref idref="DRAWINGS">FIG. 5</figref>, the tension roller <b>15</b>C may position upside the opposing roller <b>15</b>B in <figref idref="DRAWINGS">FIG. 8</figref>. However, it is not-substantial difference. Thus, the same legends are assigned to respective sections of the fixing apparatus of <figref idref="DRAWINGS">FIG. 8</figref> in accordance with the sections of the fixing apparatus of <figref idref="DRAWINGS">FIG. 5</figref>, and description of these basic construction and function may be omitted.

0082A difference between these fixing apparatuses of <figref idref="DRAWINGS">FIGS. 8 and 5</figref> is that a JIS-A hardness of the surface of a portion where the fixing belt <b>15</b>A is wound around the opposing roller <b>15</b>B is substantially the same as that of the surface of the pressure roller <b>16</b> serving as one example of the pressure applying member. Accordingly, also and similar to the fixing apparatus of <figref idref="DRAWINGS">FIGS. 6 and 7</figref> in the fixing apparatus <b>4</b> of <figref idref="DRAWINGS">FIG. 8</figref>, when only the margin M<b>1</b> in the tip of the recording member P exits from the nip “N”, the margin “M<b>1</b>” may be directed along the extension line LBB extended from the straight line LB connecting the downstream end NE and recording member transfer direction upstream end NS in the nip. In addition, a fixing member side separation device <b>19</b> for separating a recording member “P” ejected from the nip “N” from the surface of the fixing member is arranged so as to be separated from the surface of the fixing member. The gap G formed between the downstream end NE in the nip N and the tip of the fixing member side separation device <b>19</b> facing the fixing member may be set smaller than the width W of the margin M<b>1</b> formed in the tip of the recording member P in the transfer direction. Thus, similar to the fixing apparatus of <figref idref="DRAWINGS">FIGS. 7 and 8</figref>, wrapping of the recording member P around the surface of the fixing belt <b>15</b>A may be blocked. In addition, damage on the surface of the fixing belt <b>15</b>A caused by the fixing member side separation device <b>19</b> may also be blocked. Further, the recording member P ejected from the nip N can be prevented from easily curling.

0083When only the margin M<b>1</b> of the tip of the recording member P exits from the nip N in the fixing apparatus of <figref idref="DRAWINGS">FIGS. 6</figref>, <b>7</b>, and <b>8</b>, the surface hardness of JIS-A of the fixing member composed of the fixing roller <b>15</b> or fixing belt <b>15</b>A may be set to substantially the same level to that of the JIS-A of the pressure applying member composed of the pressure roller <b>16</b> in order to direct the margin M<b>1</b> almost along the extension line LBB. However, if the fixing member is formed from the fixing belt <b>15</b>A, the hardness of the surface of the fixing member may be that measured at a surface where the fixing belt contacts and is wound around the opposing roller <b>15</b>B. In brief, regardless of a difference in a shape of the fixing member, by setting a JIS-A hardness of the surface of the fixing member in the downstream end NE in the nip N to substantially the same level to that of the surface of the pressure applying member in the downstream end NE, the recording member P may be directed substantially along the extension line LBB when only the margin M<b>1</b> of the tip exits from the nip N.

0084Further, the image forming apparatus <b>1</b> is configured to form a toner image only on one side surface of the recording member P. However, an image forming apparatus capable of performing the below described functions is widely known. Specifically, the image forming apparatus is capable of transferring a toner image formed on a PC member onto one side surface of the recording member, fixing the toner image with a fixing apparatus, inverting upside down arid transferring the recording member again to the PC member, transferring a toner image formed on the PC member onto the other surface of the recording member, and fixing the toner image with the fixing apparatus. When toner images respectively formed on the one and other sides of the recording member require to be distinguished, the former may be termed as a first toner image, and the latter may be termed as a second toner image.

0085When the second toner image is transferred through the nip and is fixed, the first toner image fixed to the one side surface of the recording member may also pass and contact the pressure applying member. At that time, since the pressure applying member is also heated, the heat fuses the first toner image. As a result, the recording member ejected from the nip may likely wrap around the pressure applying member.

0086Then, a pressure applying member side separation device <b>22</b> for separating a recording member P ejected from the nip N from a pressure applying member (a pressure roller <b>16</b> in this example) may be employed in a fixing apparatus <b>4</b> of <figref idref="DRAWINGS">FIGS. 2 and 5</figref>. In addition, a tip of the separating device <b>22</b> facing the pressure applying member may contact the pressure applying member. Such a pressure applying member side separating device <b>22</b> may be formed from a plurality of separation claws arranged in an axial direction of the pressure roller <b>16</b>, or a single sheet of sheet like separation member.

0087As illustrated in <figref idref="DRAWINGS">FIGS. 2 and 5</figref>, when the first toner image TA is fixed and carried on the one side surface, and the second toner image T to be fixed is carried on the other side surface when entering the nip N, since the first toner TA is heated and fused when the recording member P passes through the nip N, the recording member P ejected from the nip N sometimes wraps around the surface of the pressure roller <b>16</b>. However, even in such a situation, the pressure applying member side separating device <b>22</b> contacting the surface of the pressure roller <b>16</b> may separate the recording member P from the surface of the pressure roller <b>16</b>.

0088Since the tip of the pressure applying member side separating device <b>22</b> contacts the surface of the pressure applying member composed of the pressure roller <b>16</b>, the recording member attempting to wrap around the surface of the pressure roller <b>16</b> may surely be separated therefrom. At that time, as described earlier, since the surface hardness of the pressure roller <b>16</b> is higher than that of the fixing roller <b>15</b>, and accordingly, the surface of the pressure roller <b>16</b> is hardly damaged, the surface of the pressure roller <b>16</b> can be prevented from being damaged by the pressure applying member side separating device <b>22</b>.

0089Further, as illustrated in <figref idref="DRAWINGS">FIGS. 6 to 8</figref>, when only the tip margin M<b>1</b> of the recording member P exits from the nip N, the tip margin M<b>1</b> may be directed almost along the extension line LBB. Beside, the pressure applying member side separation device <b>19</b>A may be arranged for being separated from the surface of the pressure applying member and separate the recording member P ejected from the nip N. In addition, the gap G formed between the downstream end NE and the tip facing the pressure applying member in the pressure applying member side separation device <b>19</b>A is set smaller in size that the width W of the margin M<b>1</b> formed in the downstream end of the recording member P. Such a pressure applying member side separation device <b>19</b>A may be shaped in appropriate. However, it can be formed from a separation member <b>20</b>A made of a sheet.

0090When the recording member P entering the nip N carries the first toner image TA already fixed on to one side surface and the second toner image T to be fixed by the fixing apparatus <b>4</b> on the other side surface, and passes through the nip N, the first toner image TA fuses. However, similar to the fixing member side separation device <b>19</b>, the pressure applying member side separation device <b>19</b>A may prevent the recording member from wrapping around the surface of the pressure roller <b>16</b>. Further, since the pressure applying member side separation device <b>19</b>A is distanced from the surface of the pressure roller <b>16</b>, a problem of damaging the surface may be blocked.

0091Further, as illustrated in <figref idref="DRAWINGS">FIGS. 6 to 8</figref>, since the above-described fixing member side and pressure applying member side separation devices <b>19</b> and <b>19</b>A are simultaneously employed, wrapping of the recording member P around either the fixing member or pressure applying member can be blocked. A fixing apparatus <b>4</b> of <figref idref="DRAWINGS">FIG. 9</figref> may also be configured to block wrapping of a recording member around a pressure applying member. A basic configuration and operation of the fixing apparatus of <figref idref="DRAWINGS">FIG. 9</figref> may be similar to that of the fixing apparatus of <figref idref="DRAWINGS">FIG. 2</figref>. Differences therebetween may be that a JIS-A surface hardness of the pressure roller may be set lower than that of the fixing roller <b>15</b>, and the fixing roller <b>15</b> may deform the pressure roller <b>16</b> with a pressure. Further, a heater may be disposed in the pressure roller <b>16</b>, and a heater <b>17</b> may also be disposed in the fixing roller <b>15</b> so as to heat the fixing roller <b>15</b>. The nip N may be maintained at an appropriate temperature suitable for fixing. A difference in a JIS-A surface hardness between of the fixing roller <b>15</b> and pressure roller <b>16</b> may also be maintained at from about 20 to about 40 degree. The fixed first toner image TA may be carried on the one side surface of the recording member P, and the second toner image T to be fixed by the fixing apparatus <b>4</b> may be carried one the other side surface, and such a recording member P may be transferred into the nip N between the fixing and pressure rollers <b>15</b> and <b>16</b> in a direction as shown by an arrow A. Thus, the second toner image T may be fixed while passing through the nip N.

0092At that time, the toner of the first toner image TA is heated and fused. However, to prevent the recording member P from wrapping around the surface of the pressure roller <b>16</b> due to melting toner of the first toner image, the pressure applying member side separation device <b>19</b>A may be arranged so as to separate the recording member exiting from the nip N from the surface of the pressure applying member formed from the pressure roller <b>16</b> separated from the surface of the pressure applying member. The condition illustrated in <figref idref="DRAWINGS">FIG. 9</figref> is when the entire margin M<b>1</b> of the transfer direction tip of the recording member P has just exited from the nip N. However, the gap GA formed between the downstream end NE of the nip N and the tip of the pressure applying member side separation device <b>19</b><i>a</i>, which faces the pressure applying member, may be set smaller than the width W of the margin MI. Such a pressure applying member side separation device <b>19</b><i>a </i>may also be formed from a sheet like separation member <b>20</b>A.

0093As illustrated in <figref idref="DRAWINGS">FIG. 9</figref>, since the surface hardness of the fixing roller <b>15</b> is set higher than that of the surface of the pressure roller <b>16</b>, when only the margin M<b>1</b> exits from the nip N, the margin M<b>1</b> may take a posture along the surface of the fixing roller <b>15</b>, and is largely distanced from the surface of the pressure roller <b>16</b>. Namely, when the margin M<b>1</b> exits from the nip N, the margin M<b>1</b> may be directed to the fixing member side across the extension line LCC extended from the straight line LC toward the recording member transfer direction side, which straight line LC is drawn from the downstream end NE to the upstream end NS.

0094When the image region IA of the recording member P (see <figref idref="DRAWINGS">FIG. 4</figref>) exits from the nip N, since the toner of the second toner image T carried on the other side surface fuses, the recording member P may sometimes be pulled toward the fixing roller <b>15</b> side. However, since the toner of the first toner image TA carried on the one side surface also fuses, the recording member P may also sometimes be pulled toward the pressure roller <b>16</b> side. Since the gap GA is smaller than the width W of the margin M<b>1</b>, in addition, the surface hardness of the pressure roller <b>16</b> is lower than that of the fixing roller <b>15</b>, and the margin M<b>1</b> does not adhere to the surface of the pressure roller <b>16</b> due to toner adhesive force when only exiting from the nip N, the regarding member P almost never wraps around the surface of the pressure roller <b>16</b> even when pulled toward the pressure roller <b>16</b> side. In addition, since the pressure applying member side separation devise <b>19</b>A is distanced from the surface of the pressure roller <b>16</b> having a low surface hardness and easily damaged, the damage can substantially be blocked.

0095In addition, the fixing member side separation device <b>22</b>A may be a sheet like separation member contact the surface of the fixing roller <b>15</b>. Thus, even though the recording member P ejected from the nip N adheres to the surface of the fixing roller <b>15</b>, the recording member P may immediately be separated from the surface of the fixing roller <b>15</b> by the fixing member side separation device <b>22</b>A, and does not wrap around the surface of the fixing roller <b>15</b>. Even if the fixing member side separation device <b>22</b>A contact the surface of the fixing roller <b>15</b>, the damage on the surface may be prevented, because the surface of the fixing roller <b>15</b> is harder. Thus, by contacting the fixing member side separation device <b>22</b>A to the surface of the fixing roller <b>15</b>, wrapping of the recording member P around the fixing roller <b>15</b> may credibly be blocked. The recording member P exiting from the nip N may be guided and is transferred by the pressure applying member side separation device <b>19</b>A and guide member <b>21</b>A arrange above the pressure applying member side separation device <b>19</b>A. As described above, wrapping of the recording member P around both the fixing and pressure rollers <b>15</b> and <b>16</b>, and damage on both of the surfaces of the fixing and pressure rollers <b>15</b> and <b>16</b> can be blocked. As a result, quality of the first and second toner images of the recording member P passing through the nip N may avoid from being decreased.

0096One example of a specific configuration of the fixing apparatus <b>4</b> may now be described with reference to <figref idref="DRAWINGS">FIG. 9</figref>. An iron hollow roller having a releasing layer on its outer surface, whose outer diameter is 40 mm and thickness is 0.6 mm, may be employed for a fixing roller <b>15</b>. An aluminum core metal, whose outer diameter is 40 mm, carrying a foam silicone rubber layer whose thickness is 5 mm, on .the core metal and including a PFA tube having thickness of 30 μm around the foam silicone rubber layer may be employable for a pressure roller <b>16</b>. In this configuration, since no elastic layer is formed on the fixing roller <b>15</b>, heat capacity of the fixing roller <b>15</b> may be small, and accordingly, a startup time required when the fixing roller <b>15</b> reaches a prescribed temperature available for fixing from when a power supply is turned ON may be minimized. In addition, a relation that a surface hardness of a fixing member is higher than that of a pressure applying member may be applicable to a configuration where a fixing member is formed from a fixing belt as illustrated in <figref idref="DRAWINGS">FIG. 10</figref>. A basic thought of the fixing apparatus <b>4</b> of <figref idref="DRAWINGS">FIG. 10</figref> may be similar to the fixing apparatus of <figref idref="DRAWINGS">FIG. 9</figref>.

0097Briefly, a fixing member heated by the heaters <b>17</b>A and <b>17</b>B may be formed from a fixing belt <b>15</b>A wound and rotated around a guide member formed from an opposing roller <b>15</b>B and a tension roller <b>15</b>C in this example, in a direction shown by an arrow B. A pressure applying member pressure contacting the fixing member may be formed from a pressure roller <b>16</b> contacting at least one guide members, i.e., the opposing roller <b>15</b>B in this example, via the fixing belt <b>15</b>A, and rotating in a direction shown by an arrow. The JIS-A surface hardness of the pressure roller <b>16</b> may be set lower than that on a portion of the fixing belt contacting the opposing roller <b>15</b>B.

0098The recording member P carrying a second toner image T to be fixed may pass through a nip N formed by pressure contact of the fixing belt <b>15</b>A and pressure roller <b>16</b> with the second toner image T being directed to contact the fixing belt <b>15</b>A. When only a margin M<b>1</b> formed in the transfer direction tip of the transferred recording member P exits from the nip N, the tip margin M<b>1</b> may be directed to the fixing member (i.e., the fixing belt <b>15</b>A) side across an extension line LCC extended from the straight line LC drawn from the downstream end NE to the upstream end NS of the nip N in the transfer direction.

0099As shown by an arrow A, the first toner image TA having already been fixed may be formed on the one side surface of the recording member P entering into the nip N. In addition, the pressure applying member (i.e., the pressure roller <b>16</b>) side separation device <b>19</b>A may be arranged separately from the surface of the pressure applying member so as to separate the recording member P ejected from the nip N. Further, a gap GA formed between a downstream end NE of the nip N and a tip of the pressure applying member side separation device <b>19</b>A, which faces the pressure applying member, may be set smaller in size than the width “W” of the margin M<b>1</b> formed in the tip of the recording member P in the transfer direction A. Owing to this configuration and similar to the fixing apparatus of <figref idref="DRAWINGS">FIG. 9</figref>, the recording member P may avoid wrapping around the pressure roller <b>16</b>. In addition, the pressure applying member side separation device <b>19</b>A may also be blocked damaging the pressure roller having slow surface hardness. In addition, the fixing member side separation device <b>22</b>A contacting the fixing belt <b>15</b>A may block the recording member P from wrapping around the fixing belt <b>15</b>A. The recording member P ejected from the nip N may then be guided and transferred by the pressure applying member side separation device <b>19</b>A together with the member <b>21</b>A.

0100Also in the cases of the fixing apparatuses of <figref idref="DRAWINGS">FIGS. 9 and 10</figref>, the JIS-A surface hardness of the fixing member at the downstream end NE may be set higher than that of the pressure roller side at the same position NE, so that the tip blank “M<b>1</b>” is directed to the fixing member side across the extension line LCC when only exiting from the nip “N”. In addition, since the fixing member side separation device <b>22</b>A contacts the fixing member so as to separate the recording member P ejected from the nip N from the fixing member, wrapping of the recording member around the fixing member may efficiently be blocked. In addition, since the surface of the fixing member is hard, damage on the fixing member, which is caused by the fixing member side separation device <b>22</b>A, can be blocked. Further, in the above-described respective embodiments, the gap G formed between the downstream end NE of the nip N and the tip of the fixing member side separation device <b>19</b> is set to be smaller in size than the width W of the margin M<b>1</b>, the tip of the fixing member side separation device <b>19</b> may position in the vicinity of the fixing member. In order to precisely arrange the fixing member side separation device <b>19</b> in such a position, the below-described configuration may preferably be adopted.

0101<figref idref="DRAWINGS">FIG. 11</figref> illustrates an exemplary configuration for positioning a fixing member side separation device <b>19</b> composed of a sheet like separation member <b>20</b> with regard to a fixing roller <b>15</b> of <figref idref="DRAWINGS">FIGS. 2 and 6</figref>. As illustrated in <figref idref="DRAWINGS">FIG. 11</figref>, a pair of gap holding members <b>29</b> may be secured to respective ends of the separation member <b>20</b> in the longitudinal direction, i.e., respective ends of the fixing member side separation devices in the direction perpendicular to a transfer direction of the recording member. In addition, the respective gap holding members <b>29</b> may be supported by the supporting member <b>31</b> via a pair of screws <b>30</b>. The supporting member <b>31</b> may be biased against a surface of a fixing roller <b>15</b> by a pair of pressure applying members <b>32</b> such as compression springs. Thus, both the gap holding members <b>29</b> may contact the surface of the fixing roller <b>15</b>. As illustrated in <figref idref="DRAWINGS">FIG. 12</figref>, both the gap holding members <b>29</b> may contact recording member non-passing areas PA on the fixing roller <b>15</b>, i.e., longitudinal direction end regions on the fixing roller, where the recording member does not pass through. As a result, the above-described gap G between a tip of the fixing member side separation device <b>19</b>, which opposes a recording member passing region, and the surface of the fixing roller <b>15</b> may precisely be maintained.

0102The position of the surface of the fixing roller <b>15</b> is not constant because of receiving influence of heat expansion and eccentricity of the roller. However, when the fixing member side separation device <b>19</b> is positioned in the above-described manner, the gap G can be maintained substantially constant along the entire longitudinal direction of the fixing member side separation device <b>19</b>. In addition to that, the gap holding members <b>29</b> contact the recording sheet non-passing areas PA, the gap holding members <b>29</b> may almost never damage the recording member passing area PB. In addition, influence from the gap holding member <b>29</b> contacting the fixing roller <b>15</b> may be avoided.

0103Similar to those described above, when the fixing members of <figref idref="DRAWINGS">FIGS. 5 and 8</figref> are each formed from the fixing belt <b>15</b>A, both the interval between the fixing member side separation device <b>19</b> and surface of the fixing belt <b>15</b>A, and the gap G can be correctly regulated by enabling the gap holding member <b>29</b> to contact the recording member non-passing area.

0104By employing the gap holding member in respective ends of the fixing member side separation device in the direction perpendicular to the recording member transfer direction, while enabling the respective gap holding members to contact the recording member non-passing areas, and holding the interval between the tip of the fixing member side separation device and surface of the fixing belt <b>15</b>A in the above-described manner, the tip of the fixing member side separation device can readily be approximated and correctly positioned regarding the fixing member. Also, in order to position the pressure applying member side separation device <b>19</b>A when approximating the surface of the pressure roller <b>16</b>, the configuration illustrated in <figref idref="DRAWINGS">FIGS. 11 and 12</figref> may be similarly employable. Specifically, instead of using for the fixing roller <b>15</b> of <figref idref="DRAWINGS">FIGS. 11 and 12</figref>, it may be arranged for the pressure roller <b>16</b> illustrated in <figref idref="DRAWINGS">FIGS. 9 and 10</figref>. In this way, the gap holding members are arranged in respective ends of the pressure applying member side separation device in the direction perpendicular to the recording member transfer direction, and the respective gap holding members can contact the recording member non-passing area of the fixing member. As a result, the gap between the tip of the pressure applying member side separation device and surface of the pressure applying member may be precisely maintained, and the pressure applying member side separation device can be approximated and is correctly positioned in relation to the surface of the pressure applying member. In addition, since the gap holding member contacts the recording member non-passing area, the recording member non-passage area can avoid from a problem of damaging. Instead if using the sheet like separation members <b>20</b> and <b>20</b>A, a separation device formed from a separation claw composed of a single plate member or a plurality of separation claws arranged along the surfaces of the fixing and/or pressure applying members can be employed for the fixing member side separation device <b>19</b> and the pressure applying member side separation device <b>19</b>A, each of which are distanced from the fixing and pressure applying members. However, since the fixing member side and the pressure applying member side separation devices <b>19</b> and <b>19</b>A are arranged separately from the fixing and pressure applying members, respectively, one sheet like or plate like separation member as illustrated in the drawing can be employed for each of the respective separation devices <b>19</b> and <b>19</b>A. When the separation device contacts the surface of the fixing or pressure applying member, a separation device formed from a plurality of separation claws is necessarily employed, and a spring should adjust the pressure of the respective separation claws contacting the respective fixing and pressure applying members so as to even out the contact pressure. However, since both the fixing member side and the pressure applying member side separation devices <b>19</b> and <b>19</b>A do not contact the fixing and pressure applying members, respectively, the contact pressure does not need adjustment, and these fixing member side separation device <b>19</b> and pressure applying member side separation device <b>19</b>A can be formed form a single separation and are adopted. By constructing respective separation devices <b>19</b> and <b>19</b>A in this manner, the number of parts and the cost therefor can be decreased. In addition, since a spring for adjusting contact pressure of the fixing member side separation device <b>19</b> and pressure applying member side separation device <b>19</b>A against the fixing and pressure applying members, respectively, can be omitted, both the fixing member side separation device <b>19</b> and pressure applying member side separation device <b>19</b>A can be integrated with a guide member for recording member use and a casing of the fixing apparatus (not shown). Further, as illustrated in <figref idref="DRAWINGS">FIG. 11</figref>, if one or more openings <b>36</b> are formed in a separation member <b>20</b> forming the fixing member side separation device <b>19</b> so as to ventilate, water vapor generated from a recording member heated in the nip N may be evacuated upward via the openings <b>36</b>. Thus, a problem that the water vapor is condensed on the recording member P, and thereby a decrease in quality, may be avoided. Similarly, one or more openings for ventilation may be formed in a separation section <b>20</b>A forming a pressure applying member side separation device <b>19</b>A, water vapor generated from a recording member may similarly be evacuated upwardly via the openings.

0105As illustrated in the drawing, both the fixing member side separation device <b>19</b> and the pressure applying member side separation device <b>19</b>A are made from sheet like separation members <b>20</b> and <b>20</b>A, and, in particular, if those thickness are thin, waving due to heat expansion of these separation members, and deformation due to contacting of the recording member to the separation members <b>20</b> and <b>20</b>A may arise. As a result, a gap between each of the separation members <b>20</b> and <b>20</b>A and fixing member or pressure applying member may likely be uneven in a longitudinal direction of the separation member. Then, if both the fixing member side separation device <b>19</b> and the pressure applying member side separation device <b>19</b>A are made from sheet like separation members <b>20</b> and <b>20</b>A, a tension applying device for pulling the separation members <b>20</b> and <b>20</b>A in a direction perpendicular to a recording member transfer direction may preferably be employed. Then, the above-described problem may be avoided.

0106The separation member <b>20</b> may be secured to the gap holding member <b>29</b> via respective ends in the longitudinal direction, and the both of the gap holding members <b>29</b> are supported by the supporting members <b>31</b> via screws <b>30</b>. However, the separation member <b>210</b> may be maintained flat by screwing the screws <b>30</b>, and pulling the separation member <b>20</b> in the direction shown by an arrow, and applying a tension thereto. Thereby, a gap between the separation member <b>20</b> and fixing roller <b>15</b> can be maintained constant. In such a manner, the screws <b>30</b> may constitute an exemplary tension-applying device for pulling the separation member. A tension-applying device for pulling the separation member <b>20</b>A of the pressure applying member side separation device <b>19</b>A may similarly be configured.

0107For the sheet like separation members <b>20</b> and <b>20</b>A, a thin plate of heat resistance plastic or metal may be employed. For example, fluorine plastic, and polyimide having a thickness of 0.1 mm may be employed. In addition, if a metal sheet or metal plate member having a thickness of 0.2 mm is employed for the sheet like separation members <b>20</b> and <b>20</b>A, since rigidity is enhanced, a gap between the separation member and fixing member or pressure applying member can be maintained constant without employing the above-described tension applying device.

0108Further, in order to credibly avoid wrapping of the recording member around either the fixing or pressure applying member in the above-described respective fixing apparatuses, a release agent such as silicone oil can be coated on each of these apparatuses. However, when employing such a configuration, the oil adheres and soils the recording member, and maintenance may be complex due to oil coating. In addition, a coating member for coating oil may be necessitated, thereby resulting in a cost increase for the fixing apparatus.

0109Then, if wax including toner is used so as to form a toner image with plastic and coloring agent, so called oil less image formation may be realized without coating release agent. As a result, the above-described problem can be removed.

0110The above-described respective configurations may be widely applied to fixing apparatuses other than those described above. Even though the guide roller formed from a roller <b>15</b>B and tension roller <b>15</b>C are employed for a guide member for winding the fixing belt <b>15</b><i>a </i>in the fixing apparatus of <figref idref="DRAWINGS">FIGS. 5</figref>, <b>8</b>, and <b>10</b>. However as illustrated in <figref idref="DRAWINGS">FIG. 13</figref>, a guide member configured by a pair of the guide rollers <b>33</b> and <b>34</b>, and heater <b>35</b> can be employed in the fixing apparatus <b>4</b> so as to wind a fixing belt <b>15</b>A therearound. The heater <b>35</b> may include a pair of electrodes, and a resisting member arranged between the electrodes and contacting the internal surface of the fixing belt <b>15</b>A. Thus, the resisting member may be enabled to generate heat when receiving power supply thereby heating the fixing belt <b>15</b>A. Also in such a fixing apparatus, various configurations described earlier with reference to <figref idref="DRAWINGS">FIGS. 5</figref>, <b>8</b> and <b>10</b> may be adopted.

0111In addition, a pressure belt wound and driven by a plurality of guide members as described earlier can configure the pressure applying member. In such a case, when the pressure belt portion wound around the guide member contacts and forms a nip with the fixing member, the JIS-A surface hardness of the pressure belt may be obtained by measuring a surface of the pressure belt portion contacting and wound around the guide member.

0112Another embodiment is now described with reference to <figref idref="DRAWINGS">FIGS. 14 to 24</figref>. As illustrated in <figref idref="DRAWINGS">FIGS. 14 and 15</figref>, a fixing apparatus <b>110</b> is of a roller type that includes an oil strainer formed from a plastic parent material in which wax is included and dispersed as release agent. The fixing apparatus <b>110</b> may include a fixing roller <b>125</b> serving as a rotational fixing device, and a pressure roller <b>126</b> pressure contacting the fixing roller <b>125</b> as a pressure device. Also provided may be a cleaning roller <b>127</b> for removing paper dust or the like remaining on the surface of the fixing roller <b>125</b>, and a separation sheet <b>128</b> arranged in an exit side of the nip of a fixing roller <b>125</b>. Each of the rollers <b>125</b>, <b>126</b> and <b>127</b> maybe pivotably secured to a fixing apparatus use base frame secure to a portion of a wall surface of an image forming section <b>101</b>A. The separation sheet <b>128</b> may be secured to a fixing apparatus use base frame <b>129</b> via a guide member <b>130</b> (see <figref idref="DRAWINGS">FIGS. 17 and 18</figref>) as described later in detail. Further, a transfer guide member <b>131</b> may be attached to a portion of the fixing apparatus use base frame <b>129</b>, which opposes to the end of a second transfer apparatus <b>109</b>, and guide and lead a recording member carrying a not yet fixed toner image to a nip N formed between the fixing and pressure rollers <b>125</b> and <b>126</b>.

0113As illustrated in <figref idref="DRAWINGS">FIG. 16</figref>, the fixing roller <b>125</b> may include a core metal <b>251</b> as a roller section, and an elastic layer <b>252</b> wrapping around the core metal <b>251</b>, and a release agent layer <b>253</b> each integrally connected around the roller section.

0114The fixing roller <b>25</b> may have a diameter of 60φ, for example. Also included may be a ring like elastic layer <b>252</b> molded and processed for obtaining a nip width “LO” around the outer surface of a Fe core metal <b>251</b>. Such a ring like elastic layer <b>252</b> may be made of heat resistance elastic member such as liquid type foam silicone rubber. The ring like elastic layer <b>252</b> may include a release agent ring state layer <b>253</b> so as to wrap and integrally is coated on the outer surface of the ring like elastic layer <b>252</b>. Such a release agent ring state layer <b>253</b> may be formed from heat resistance plastic having a prescribed intensity in conjunction with releasability. A halogen type heater <b>254</b> may be arranged inside the metal core of the fixing roller <b>25</b> so as to accelerate increasing in temperature of the fixing roller.

0115As illustrated in <figref idref="DRAWINGS">FIG. 15</figref>, a thermistor <b>132</b> may be arranged slidably contacting the surface of the fixing roller <b>25</b>. A temperature control section <b>119</b> serving as a portion of an image processing section may be configured to adjust a surface temperature of the fixing roller <b>25</b> within a prescribed range based upon detected temperature. Material having heat resistance and small surface energy may be employed as a release layer <b>253</b> of <figref idref="DRAWINGS">FIG. 16</figref>. For example, heat resistance silicone plastic, and fluorine plastic such as poly-tetra-fluoro ethylene (PTFE), PFA, FEP, etc., may be employed as a heat resistance tube.

0116A surface hardness of the fixing roller <b>25</b> may be around 30 to 50 Hs (Asker: measurement in conformity to Japanese Rubber Association Standard). The pressure roller <b>26</b> may include a heat resistance elastic layer <b>262</b> such as silicone rubber, and a surface release layer <b>263</b> forming an endless pressure surface Fc made of fluorine plastic on the outer surface of an Al or Fe core metal <b>261</b>. In this example, the surface hardness of the pressure roller <b>26</b> may be higher than that of the surface of the fixing roller <b>25</b>, and accordingly, a fixing use nip having a width LO is formed with its both ends being concave downward in a contact portion of the fixing belt and pressure roller to improve separation performance of the recording sheet having the toner. In the embodiment, a thickness of the elastic layer <b>262</b> may amount to about 0,5 mm to 2 mm, and the surface hardness may be 70 to 90 Hs (Asker C type). A halogen heater <b>624</b> may be arranged in the pressure roller <b>126</b> so as to accelerate increasing in temperature thereof. As illustrated in <figref idref="DRAWINGS">FIG. 15</figref>, a thermistor <b>133</b> may be attached slidably contacting the surface of the pressure roller <b>126</b>. Thus, a temperature control section <b>19</b> constituting an image processing section may be configured to adjust a surface temperature of the pressure roller <b>125</b> within a prescribed range based upon detected temperature information.

0117A journal <b>261</b>′ integral with an end of the core metal of the pressure roller <b>126</b> may be movably attached to the fixing apparatus use base frame <b>129</b> so as to move up and down in order for the pressure applying roller <b>126</b> to separate from the fixing roller <b>125</b>. Specifically, the journal <b>261</b>′ may be supported by a lever <b>134</b> via a pivot section <b>265</b> pivotally supporting the journal <b>261</b>′. A key axis of the lever <b>134</b> may pivotally be connected to the fixing apparatus use base frame <b>129</b> and a swinging end thereof is pivotally engaged with a tension spring <b>35</b> whose one end is engaged with the fixing apparatus use base frame <b>29</b>.

0118Thus, the lever <b>134</b> may elastically receive upward tension force. Thus, the tension spring <b>135</b> may enable the pressure roller <b>26</b> to pressure contact the fixing roller <b>25</b>. The fixing apparatus <b>110</b> may include a rotational driving unit (not shown) that transmits a rotational driving force to the pressure roller <b>126</b>. Such rotational driving force can be transmitted to the fixing roller <b>125</b>. As illustrated in <figref idref="DRAWINGS">FIGS. 15 and 16</figref>, a separation sheet <b>128</b> may be arranged in an exit side “g” of the nip of the fixing roller <b>125</b><b>50</b> as to avoid the recording member from wrapping around the fixing roller <b>125</b>. As illustrated in <figref idref="DRAWINGS">FIGS. 17 and 18</figref>, a diameter of a paper transfer station of the fixing roller <b>125</b> may be <b>60</b>, for example, and include a pair of journals <b>251</b>′ (i.e., an integral portion with the both end portions of the metal core <b>251</b>) having <b>30</b> at both ends, respectively. The journal <b>251</b>′ may be supported by a bearing section <b>301</b> of the guide members <b>130</b> via bearings (not shown).

0119The pair of guide member <b>130</b> may symmetrically be shaped. Each of the pair of guide members <b>130</b> may be formed from a bearing section <b>301</b> pivotally supporting the journal <b>251</b>′, and an attaching wall <b>302</b> disposed at its one side and secured to the fixing apparatus use base frame <b>129</b> via the bracket <b>136</b>, and a sheet reception section <b>303</b> extending from the other end of the bearing section <b>301</b>. Since the pair of left and right guide members <b>30</b> is secured to the fixing apparatus use base frame <b>129</b> via the bracket <b>136</b>, it may not rotate even if the fixing roller <b>125</b> rotates. The sheet reception section <b>303</b> may be a thick plate like and form a concave sheet groove <b>301</b> while maintaining a gap “j” with the other surface f<b>1</b> of the bearing section <b>304</b> at an upper opening.

0120As illustrated in <figref idref="DRAWINGS">FIGS. 18A and 18B</figref>, the separation sheet <b>28</b> may precisely be attached to prescribed positions in relation to the fixing roller <b>125</b> by inserting a separation sheet <b>128</b> along the respective grooves <b>304</b> of the pair of left and right guide members <b>130</b>. Further, the gap “j” of the respective sheet grooves <b>304</b> may have substantially the same width to a thickness of the separation sheet <b>128</b>. A screw hole <b>305</b> may be formed at an upper end of the sheet reception section <b>303</b> so as to receive a sheet fastening use screw for securing the separation sheet <b>128</b> inserted and supported by the sheet groove <b>304</b>. The separation sheet <b>128</b> may be a sheet like having a thickness about 0,1 to 0,2 mm made of such as a heat resistance plastic sheet, a metal thin sheet, etc.

0121The separation sheet may include a straight portion <b>282</b> and a concave portion <b>283</b> having a curvature almost along the outer diameter shape of the release layer. The separation sheet may maintain a prescribed gap “d” at its tip with a releasing layer in the vicinity thereof. Also include may be a tip <b>281</b> of a tip of the concave section <b>283</b>. The tip <b>281</b> may be distanced from the nip exit end of the fixing roller by a prescribed length L<b>1</b>. Further, typically, a distance from a tip of a recording paper S to that of an image may be called as a tip blank width as described earlier. However, when the paper exits from the nip exit “g”, the recording sheet “S” may indeed not wrap around the fixing roller <b>25</b> unless the tip blank width exits from the nip.

0122However, a mechanism likely withdrawing and wrapping the recording sheet “S” around the fixing roller <b>125</b> due to adhesive force caused by the fixing roller <b>125</b> just when the image tip exits from the exit “g” may be employed. To avoid wrapping of the recording sheet “S”, if the distance “L<b>1</b>” from the tip of the separation sheet <b>128</b> and that of the nip exit “g” (i.e., a distance from the end of the nip exit “g”) is smaller than the tip blank width, the recording sheet S may not wrap around the fixing roller <b>125</b> and relatively readily be separated by the separation sheet <b>128</b>. Then, the recording sheet may be transferred and ejected onto an ejection tray by the ejection rollers <b>138</b> and <b>139</b>. Since the tip blank width in the fixing apparatus <b>110</b> of <figref idref="DRAWINGS">FIG. 14</figref> may be set to 3 mm, for example, the tip portion <b>281</b> of the separation sheet <b>128</b> may be attached so that the distance L<b>1</b> from the nip exit end can amount less than 3 mm.

0123The separation sheet <b>128</b> may generally have substantially the same thickness at its tip <b>281</b> to the other. However, as illustrated in <figref idref="DRAWINGS">FIG. 19</figref>, a ridge of the tip portion <b>281</b> facing the separation layer <b>253</b> may be formed in a sharp edge “e” having an angle φ. Thus, the recording sheet tip easily is trapped even if the tip portion <b>281</b> has substantially the same thickness to the other. However, if the tip portion <b>281</b> of the separation sheet <b>28</b> forms the ridge “e”, the ridge edge “e” may more credibly separate the recording sheet tip from the fixing roller <b>125</b> even if a thin recording sheet is ejected while wrapping around the fixing roller <b>25</b> from the nip exit “g”.

0124Further, a surface roughness of the edge section “e” may be less than 0.2 μm (Ra). Thus, the recording member separation performance may credibly be maintained, and durability of the fixing roller <b>25</b> may be improved. In addition, thin film coating can be performed with such as fluorine plastic on the surface of the separation sheet <b>128</b>, so that damaging on the fixing roller <b>125</b> can be lowered even if the separation sheet <b>128</b> contacts the fixing roller <b>125</b>, in particular, in the release layer <b>253</b>. In addition, the separation sheet <b>128</b> and releasing layer <b>253</b> of the fixing roller <b>125</b> of <figref idref="DRAWINGS">FIGS. 15 and 16</figref> may be distanced from each other by a gap “d”. The gap “d” may ideally preferably be 50 μm not to enter into the gap between the fixing roller <b>125</b> and separation roller <b>128</b> even if the thinnest sheet wraps therearound.

0125However, adjusting the gap to less than 50 μm may practically be difficult due to a straightness of the tip portion of the separation sheet <b>128</b>, and vibration of the fixing roller when rotated. If the gap “d” is narrowed, the fixing roller <b>125</b> may dispose heat and lower its surface temperature as another problem when the fixing roller <b>125</b> contacts or is in the vicinity of the separation sheet <b>128</b>. According to the present embodiment, a pair of left and right guide members <b>130</b> of <figref idref="DRAWINGS">FIG. 17</figref> may be employed, and the gap “d” may preferably be set to about 0.5 mm considering parts prevision. Now, a process where a superimposed multi-color or mono-color toner image not yet fixed is fixed by fixing and pressure rollers onto a recording sheet S may be described with reference to <figref idref="DRAWINGS">FIGS. 20 to 24</figref>.

0126The toner image “t” on a recording sheet S having reached the fixing apparatus <b>110</b> may be heated by the fixing roller <b>125</b> up to a level where its viscosity is lowered, and then penetrates into a texture of the recording sheet by an operation of the pressure force of the pressure roller <b>115</b>. The toner may then be firmly fixed to the sheet texture when cooled and consolidated. However, if temperature of a toner layer is less than its softening temperature Ts when separated from the fixing roller <b>125</b>, the toner plastic may not sufficiently be softened, and accordingly, not penetrate into the texture of the sheet S, thereby resulting in insufficient fixing intensity.

0127In contrast, if the temperature of a toner layer is less than its flowage starting temperature Tf when separated from the fixing roller <b>25</b>, the toner plastic viscosity may be too low, and accordingly, releasability of the toner from the release layer <b>253</b> of the fixing roller <b>25</b> may be insufficient even though sufficiently penetrating into the texture of the recording sheet S. In addition, a problem such as offset or wrapping may arise on the fixing roller <b>25</b>. Accordingly, a control temperature for fixing maybe determined so that a toner layer surface temperature after fixing will fall within a range from Ts to Tf.

0128Preferably, a control system may be used if its temperature deviation is small at around the its center area.

0129Even if fixing from thin to thick sheets by substantially the same temperature, since heat capacity of the sheet is different from the other, the higher the toner layer surface temperature after fixing is, the thinner the sheet is, vice versa. As a result, even the offset phenomenon does not arise when the thin sheet passes, an adhesive force between surfaces of the respective fixing and pressure rollers may be large. In addition, separation after passage of the recording sheet through the nip may be difficult, and in the extreme case, the tip may wrap around the curvature of the fixing roller <b>25</b> and is carried. Depending upon the magnitude of the adhesive power, when the tip is slightly peeled off, the recording sheet may be withdrawn by its gravity. However, a certain portion may not be peeled off and wraps therearound. Such adhesive power have been known to vary in accordance with changes in environment, toner adhering amount, and temperature of a fixing roller <b>125</b> or the like. Among these, a wrapping phenomenon of a thin sheet likely wrapping around a fixing roller is now described.

0130After the recording sheet S is sand witched into the nip between the fixing and pressure rollers <b>125</b> and <b>115</b>, the toner image may be fixed onto the recording sheet S while receiving operations of heat and pressure. A nip shape formed by the fixing and pressure rollers <b>25</b> and <b>15</b> pressure contacting each other may be determined from a relation between thickness and hardness of rubber layers of the respective fixing roller <b>125</b> and pressure roller <b>126</b>.

0131As one example of embodiments, the fixing roller <b>125</b> may have a diameter of 60φ and a thickness of 2 mm for a Si rubber, and 20 degree by the JIS-A hardness standard for a rubber layer. The pressure roller <b>126</b> may also have a diameter of 60φ and a thickness of 2 mm for an Si rubber, and 30 degree by the JIS-A hardness standard for a rubber layer. In addition, the PFA tubes each having a thickness of 50 μm may be employed on the respective uppermost layers. In such a combination of rollers, if tack strength caused between the surfaces of the respective toner layer and fixing roller is negligible, the recording sheet S at the exit may slightly be directed downwardly from the horizontal line. When considering stable transfer performance, a discharge angle of the recording sheet S may preferably be directed slightly downwardly. However, if it is directed excessively downwardly, the first surface side of a duplex fixing image likely wraps around the pressure roller <b>126</b>. Thus, sufficient attention should be paid when both the fixing and pressure rollers are designed.

0132<figref idref="DRAWINGS">FIG. 20</figref> illustrates still another embodiment of a color image forming apparatus <b>101</b><i>a </i>including a fixing apparatus. Such a color image forming apparatus may have substantially the same configuration to that illustrated in <figref idref="DRAWINGS">FIG. 14</figref> except that intermediate transfer is omitted and direct transfer to the recording sheet S is performed.

0133The fixing apparatus <b>110</b><i>a </i>employed in the color copier <b>101</b><i>a </i>may now be described. The fixing apparatus <b>110</b><i>a </i>may be employed in the conventional color image forming apparatus la not coating silicone oil as release agent for the fixing belt <b>140</b> and instead using oil less toner. However, it may be applicable to a color printer, facsimile, and duplicator or the like, so that these apparatuses can improve marketable product performance as image forming apparatuses capable of credibly securing recording member separation performance if employing the fixing apparatus <b>110</b><i>a. </i>

0134As illustrated in <figref idref="DRAWINGS">FIGS. 20 and 21</figref>, the image forming apparatus may include a fixing roller <b>141</b> and heating roller <b>142</b> serving as rotatable roller type fixing devices arranged oppositely to each the other, and an endless fixing belt <b>140</b> wound around these rollers. In addition, a pressure roller <b>143</b> having an endless pressure surface Fc and contacting the fixing belt <b>140</b> may be provided so as to form a nip N. A tension roller <b>144</b> may also be provided so as to apply tension to the fixing belt <b>140</b>. In addition, a separation sheet <b>28</b><i>a </i>may be provided and oppositely arranged to the fixing belt <b>140</b>. The fixing apparatus <b>110</b><i>a </i>may heat and rotate the fixing belt <b>40</b> with a heating roller <b>142</b> in a direction shown by an arrow D as illustrated in <figref idref="DRAWINGS">FIG. 21</figref>. Then, the fixing apparatus <b>110</b><i>a </i>may heat and fuse thereby fixing a not yet fixed toner image “t” carried on the recording sheet S″ in the nip N. These rollers <b>131</b>, <b>132</b>, and <b>134</b> may be pivotally supported by a fixing apparatus use base frame <b>145</b> secured to a transfer unit U. Respective rotational shafts may be arranged in parallel.

0135A base material of the fixing belt <b>40</b> may be made of heat resistance plastic. For the heat resistance plastic, polyimede, polyamideimide, and polyetherketone (PEEK) may be employable. A thickness of the base material may preferably amount to about 30 to about 100 μm. Since the surface of the fixing belt <b>133</b> pressure contacts the non fixed toner image and recording sheet S, a surface layer having excellent releasability and heat resistance may be necessitated. Thus, a surface release layer <b>401</b> such as fluorine series plastic or the like (see <figref idref="DRAWINGS">FIG. 21</figref>) may be coated. Further, an elastic layer made of heat resistance rubber, such as silicone rubber, fluorine rubber, etc., having a thickness of from about 100 to 300 μm may be provided.

0136The heating roller <b>142</b> may be made of metal, such as AL, Fe, etc., having a diameter of from about 20φ to 30φ. The heating roller <b>142</b> may be a thin roller having a thickness (t) of from about 0.3 to 1.0 mm and include a halogen heater <b>147</b> inside thereof. Temperature of the heating roller <b>132</b> may be detected by a temperature control element <b>146</b>. Detected temperature information may be output to an image processing section <b>148</b> so as to control the heating roller to fall within a prescribed set temperature range. Thereby, it may function to heat the fixing belt <b>140</b> up to a desirable temperature.

0137Further, the heating roller <b>142</b> may double as a tension roller, so that it may be suspended by a tension spring (not shown) in a direction as shown by an arrow P<b>1</b> in the drawing. The fixing roller <b>141</b> may have a diameter of from 20φ to 30φ, and heat resistance elastic member <b>412</b> formed from heat resistance elastic member, such as form silicone rubber, liquid type silicone rubber, etc., may be provided so as to secure a nip width “L” on the outer circumference of the Fe core metal <b>411</b>. Such an elastic layer <b>412</b> may have a thickness of from about 3 mm to about 6 mm. A surface hardness of the fixing roller <b>141</b> may be from about 30 to 50 Hs (Asker-C type).

0138The pressure roller <b>43</b> may be formed from a Fe or Al core metal <b>431</b> having a heat resistance elastic layer <b>432</b> such as fluorine series rubber, silicone rubber, etc., and a surface layer <b>343</b> formed from fluorine series plastic each coated on the core metal <b>431</b>. In the current embodiment, to improve separation performance of a recording sheet carrying toner, a surface hardness of the pressure applying roller <b>143</b> may be larger than that of the fixing roller <b>141</b>. Specifically, a nip for fixing use having a width L″ may be formed between the fixing belt <b>142</b> and pressure applying roller <b>43</b> with it both ends being concave downwardly. In the current embodiment, a thickness of the elastic layer <b>432</b> of the pressure applying roller <b>143</b> may amount from about 0,5 to about 2 mm. Its surface hardness may be from about 70 to about 90 Hs (Asker-C type). A halogen heater <b>434</b> may preferably be included inside the pressure-applying roller <b>143</b> so as to accelerate increasing in temperature of the pressure-applying roller.

0139The fixing apparatus <b>110</b><i>a </i>may include a rotational driving series (not shown) so as to transmit a rotational driving force to the pressure roller <b>143</b> via a transmission device (not shown). In addition to that, the rotational driving force can be transmitted to the fixing roller <b>141</b> in a certain case. Such a fixing apparatus <b>10</b><i>a </i>may hold a nip N formed from a section where the fixing belt <b>140</b> contacts and is wound around the fixing roller <b>141</b> to where the pressure roller <b>143</b> contacts with a width of L<b>2</b>. Thus, stable transfer and fixing performances may be obtained by decreasing image crush by the nip N.

0140A separation sheet <b>128</b><i>a </i>may be oppositely arranged to a separation surface of the fixing belt <b>140</b> winding and contacting the fixing roller <b>141</b>. Such a separation sheet <b>128</b><i>a </i>may similarly be formed to that <b>128</b> of <figref idref="DRAWINGS">FIG. 14</figref>, and include a straight portion <b>282</b>, a concave portion <b>283</b>, and a tip portion <b>281</b>. Similar to the separation sheet <b>128</b>, the separation sheet <b>128</b><i>a </i>may be supported by a bracket <b>136</b> of a fixing apparatus use base frame <b>129</b> side via respective grooves of a pair of left and right guide members (See <b>304</b> of <figref idref="DRAWINGS">FIGS. 18A and 18B</figref>) pivotally supporting the fixing roller <b>141</b>.

0141The tip portion <b>281</b> of the separation sheet <b>128</b><i>a </i>may be located at a position distanced from the exit end of the nip N formed between the fixing belt <b>140</b> winding and contacting the fixing roller <b>141</b> and the pressure applying roller <b>43</b> by a prescribed length L1. In addition, the tip portion <b>281</b> of the separation sheet <b>128</b><i>a </i>may be shape similarly to that <b>128</b> of <figref idref="DRAWINGS">FIG. 14</figref>. However, repetitious explanation therefor is omitted.

0142Also in this case and similar to the separation sheet <b>28</b> of <figref idref="DRAWINGS">FIG. 14</figref>, the gap L1 may be set smaller than the tip margin, and accordingly, the recording sheet may not wrap around the fixing roller. Specifically, the separation sheet <b>128</b><i>a </i>may relatively readily separate the recording sheet, and an ejection roller <b>138</b> may transfer and eject thereof onto an ejection tray <b>121</b>.

0143The separation sheet <b>128</b><i>a </i>can be attached in a manner as illustrated in <figref idref="DRAWINGS">FIGS. 22 and 23</figref>. Specifically, an L-type bracket <b>150</b> having a similar length to a fixing roller <b>125</b> can be employed with its upper end connection portion <b>501</b> secured to a downward surface of the base frame <b>129</b> of a fixing apparatus <b>10</b><i>b </i>use. A concave sheet reception section <b>502</b> may continuously be provided in a longitudinal direction on its lower end. A surface “fe” capable of contacting an upper end of the separation sheet <b>128</b><i>a </i>may be formed on the sheet reception portion <b>502</b>. The separation sheet <b>128</b><i>a </i>may be set on the surface “fe”, and a plate <b>151</b> is laid thereon. Then, the upper end of the separation sheet <b>128</b><i>a </i>can be fastened to the sheet reception <b>502</b> via the plate <b>151</b> by a plurality of screws <b>52</b>. Thus, the separation sheet <b>128</b><i>a </i>may credibly be supported. The similar function and effect can be obtained when the fixing apparatus <b>10</b><i>b </i>employing the L-type bracket <b>150</b> of <figref idref="DRAWINGS">FIGS. 22 and 23</figref> is utilized.

0144The above-described embodiment can be employed in a mono-color image forming apparatus, facsimile, and printer or the like, and substantially the same function and effect can be obtained. Obviously numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.